The present disclosure relates to semiconductor manufacturing, and in particular, to a method of etching germanium (Ge) and Ge-rich silicon germanium (SiGe) alloys in a controlled manner. The present disclosure also relates to a chemical etchant that can be used for the controlled etching of Ge and Ge-rich SiGe alloys and a method of making such a chemical etchant.
Germanium is being considered as a possible replacement for silicon in future high performance integrated circuit (IC) manufacturing, as well as, possible use in integrated photodetectors. One of the biggest issues in processing Ge and Ge-rich SiGe alloys is the high reactivity of these materials with most conventional chemical etchants as well as reactive ion etching (RIE) chemistries.
Although there are known wet chemical etchants that can remove Ge, such as, for example, hydrogen peroxide (H2O2), there are no known etchants which remove Ge in a controlled manner. Specifically, most prior art chemical etchants employed for etching Ge-containing materials tend to roughen the Ge surface significantly rendering the Ge surface unusable for device manufacturing. In additional, most prior art chemical etchants remove Ge inhomogeneously due to a variable incubation time leading to inconsistent etch rates across the wafer.
In order to adopt Ge into any semiconductor processing flow including conventional complementary metal oxide semiconductor (CMOS) processing flows, there is a need for a well-behaved germanium etchant that does not suffer from the problems described above.